Tag Archives: IPv6

Accessing IPv6-only Resources via Legacy IP: NAT46 on a FortiGate

In general, Network Address Translation (NAT) solves some problems but should be avoided wherever possible. It has nothing to do with security and is only a short-term solution on the way to IPv6. (Yes, I know, the last 20 years have proven that NAT is used everywhere every time. 😉) This applies to all kinds of NATs for IPv4 (SNAT, DNAT, PAT) as well as for NPTv6 and NAT66.

However, there are two types of NATs that do not only change the network addresses but do a translation between the two Internet Protocols, that is IPv4 <-> IPv6 and vice versa. Let’s focus on NAT46 this time. In which situations is it used and why? Supplemented by a configuration guide for the FortiGates, a downloadable PCAP and Wireshark screenshots.

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IPv6 Crash Course @ SharkFest’22 EUROPE

Fortunately, there was a SharkFest – the “Wireshark Developer and User Conference” – this year in Europe again. I was there and gave an IPv6 Crash Course likewise. Yeah! It’s my favourite topic, you know. 75 minutes full of content, hence the name crash course.

Here are my slides as well as the video recording. If you want a crash course for IPv6, here we go:

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Why counting IPv6 Addresses is nonsense

From time to time I stumble upon Tweets about counting the number of IPv6 addresses (1 2 3). While I think it is ok to do it that way when you’re new to IPv6 and you want to get an idea of it, it does not make sense at all because the mere number of IPv6 addresses is ridiculously high and only theoretically, but has no relevance for the real-world at all. Let me state why:

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Zehn Vorteile von IPv6!

Das moderne Internetprotokoll IPv6 gilt als so komplex und umstĂ€ndlich, dass manche Administratoren beharrlich beim vertrauten, aber veralteten IPv4 bleiben. Zehn Praxisbeispiele belegen, warum viele Netzwerkanwendungen besser und kostengĂŒnstiger auf IPv6 laufen und wie Admins davon profitieren.

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Netzwerkprotokolle: Nachschlagewerk fĂŒr Wireshark

Wenn es im Netzwerk knirscht, versuchen Admins den Fehler in Analyse-Tools wie Wireshark anhand von Paketmitschnitten einzukreisen. Jedoch hat der Herr viel mehr Netzwerkprotokolle gegeben, als sich ein Admin-­Hirn in allen Details merken kann. Eine Referenzdatei, die zahlreiche korrekte Protokoll­ablÀufe enthÀlt, gibt Orientierung.

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Netzwerkmitschnitte mit tshark analysieren

Haben Sie mal Netzwerkmitschnitte untersucht, ohne zu wissen, was genau Sie suchen? Mit Wireshark wird das leicht zu einer Odyssee: Das Analysewerkzeug filtert zwar fabelhaft, reagiert bei großen Datenmengen aber schnell zĂ€h.

Was bei solchen Problemstellungen hilft ist: tshark! Ein Tool, mit welchem Sie auch große Packet Captures einfach anhand gĂ€ngiger Kriterien durchforsten können.

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#heiseshow: IPv6 setzt sich langsam durch – die wichtigsten Fragen

Ich durfte zu Gast bei der #heiseshow zum Thema IPv6 sein. In Anlehnung an die Artikelserie ĂŒber IPv6 in der c’t 7/2022, in der auch mein Artikel ĂŒber die Vorteile von IPv6-Adressen erschienen ist, ging es bei diesem Video-Podcast um gĂ€ngige Fragen zu IPv6 sowohl im Heimanwender- als auch im Enterprise-Segment. Ne knappe Stunde lief die Schose und ich empfand es als ziemlich kurzweilig. ;)

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DHCPv6 Relay Issue with Cisco ASA and Ubuntu

Some months ago, my co-worker and I ran into an interesting issue: a notebook with a newly installed Ubuntu 20.04 does only work with IPv4, but this office network is dual-stacked (IPv4 and IPv6). Other Linux clients as well as Windows and Mac systems still work fine. They all get an IPv4 configuration by DHCPv4 and an IPv6 configuration by stateful DHCPv6 from the same DHCP server, relayed by a Cisco ASA 5500-X. What’s wrong with Ubuntu 20.04?

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Publishing IPv6 NTP Servers with DHCPv6

During the last weeks, I had an interesting request to publish NTP servers to client systems by using DHCPv6 in an IPv6 only network. Our Fortigate (or me?) had to learn how to publish the information. Hence this post is not only about NTP and IPv6, but a small guide on how to walk through RFCs and how to get out the relevant information. I’m very happy I got the possibility to share my experience here. Thank you, Johannes!

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syslog-ng with TLS: Installation Guide

Some years ago I wrote a blog post called “Basic syslog-ng Installation“. While I used it myself quite often in my labs or at the customers’ sites, it shows only basic UDP transport which is both unreliable and insecure. So, let’s have a look at a fresh installation of syslog-ng with TLS support for security reasons. However, TCP and UDP as transport are covered as well for the support of legacy systems.

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Capturing – because I can: IS-IS, GLBP, VRRP

I am constantly trying to add more protocols to the Ultimate PCAP. Hence I used some time in my (old) Cisco lab to configure and capture the following protocols: IS-IS, GLBP, and VRRP. And since Alexis La Goutte sent me some CAPWAP traffic, this protocol is also added. All packets are now found in another update of the Ultimate PCAP. Here are some details:

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Certificate Transparency & Alternative Name Disclosure

Maybe you’ve heard of Certificate Transparency and its log. Citing Wikipedia: “Certificate Transparency (CT) is an Internet security standard and open source framework for monitoring and auditing digital certificates.” Basically, it gives you information about any public certificate that is issued. Besides its advantages, I thought of one possible problem as it leaks all FQDNs to the public when using TLS certificates, for example from Let’s Encrypt.

A similar problem might arise when using a single X.509 certificate with a couple of DNS names (subject alternative name SAN) from which one should be kept “private”. It will be publicly known as well.

Hence I made a self-experiment in which I generated two certificates with random names, monitoring the authoritative DNS servers as well as the IPv6 addresses of those names in order to check who is resolving/connecting to otherwise unknown hostnames. Here we go:

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UK IPv6 Council Spring 2020: Incorrect Working IPv6 Clients & Networks

I did a short presentation at the spring 2020 roundtable of the UK IPv6 Council. The talk was about a case study I did with my NTP server listed in the NTP Pool project: For 66 days I captured all NTP requests for IPv6 and legacy IP while analyzing the returning ICMPv6/ICMPv4 error messages. (A much longer period than my initial capture for 24 hours.) Following are my presentation slides along with the results.

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